class_docstr: Parse json-string of one line in annotation file to dict format.
  
  Args:
      keys (list[str]): Keys in both json-string and result dict. Defaults
          to ['filename', 'text'].
code: def __call__(self, in_str: str) -> Dict:
      line_json_obj = json.loads(in_str)
      line_info = {}
      for key in self.keys:
          if key not in line_json_obj:
              raise Exception(
                  f"key {key} not in line json {line_json_obj}"
              )
          line_info[key] = line_json_obj[key]
  
      return line_info
  
file_path: mmocr/mmocr/utils/parsers.py
imports: import json
  import warnings
  from typing import Dict, Tuple
  from mmocr.registry import TASK_UTILS
  from mmocr.utils.string_utils import StringStripper
label_desc: Use image node_id 2 for calling the LineJsonParser obj's underlying member method code with example usage: obj.__call__(in_str) and returns: line_info